This invention relates to a termination for high current electrical apparatus and, more particularly, to a termination that comprises a terminal of hard aluminum alloy and an elongated lead of relatively soft aluminum strip butt-welded at one end to the terminal.
Certain electrical apparatus, e.g., the coil assembly in a distribution-type transformer, comprises a lead of relatively soft, high-conductivity aluminum strip which must be connected to a bushing stud or the like. A bolted connection is typically used for connecting to the stud, but the soft aluminum lead does not lend itself to direct bolting to the stud because, among other things, the soft aluminum tends to cold flow and adversely affect the long-term reliability of such a joint.
For overcoming this problem, a transition element (or terminal) of hard aluminum alloy has sometimes been introduced between the soft aluminum lead and the bushing stud. Such a hard aluminum terminal can be butt-welded to the end of the strip forming the lead, but prior efforts to do this have resulted in butt-welded joints that were not as strong and damage-resistant as might be desired. In this regard, it should be noted that the terminal often does not line up very well with the bushing stud to which it is to be connected, and it then becomes necessary for the assembler to drastically bend or twist the lead-terminal assembly in order to properly position the terminal to mate with the bushing stud. Such bending and twisting can subject the weld to severe stresses which can produce undesirable cracks in it.